1. Field of the Invention
This invention relates to a suspension system for a vehicle, and more particularly to a bushing mounted on a suspension arm of a suspension system for a vehicle.
2. Description of the Prior Art
In the suspension system for a vehicle, the suspension arm is generally connected to the vehicle body by way of a rubber bushing in order to prevent transmission of vibration to the vehicle body. The stiffness of the rubber portion of the rubber bushing cannot generally be changed. Therefore, when a softer bushing is used for improvement of driving comfort, the supporting rigidity of the suspension is reduced and the steering performance is lowered when the steering wheel is turned by a large angle, and at the same time, the running stability during straight travel at high speed is adversely affected. On the other hand, when a stiffer bushing is used for improving the steering performance and the running stability during high speed straight travel, the driving comfort is sacrificed.
Though there has been proposed a suspension bushing in which a hydraulic pressure chamber is provided in the rubber portion and the deformation of the rubber portion can be controlled by controlling hydraulic pressure to be delivered to the hydraulic pressure chamber (See Japanese Unexamined Utility Model Publication No. 57(1982)-98909, for example.), this suspension bushing is disadvantageous in that the parts associated therewith are complicated in structure since the hydraulic pressure to be delivered to the hydraulic pressure chamber of the bushing is supplied from a power cylinder of a power steering system.